Golf club head having multi-layered striking face

ABSTRACT

A golf club head having a multi-layered striking face is disclosed herein. More specifically, the golf club head in accordance with the present invention has an external frontal face layer, an internal rear face layer, and an intermediary sandwiched face layer juxtaposed between the external frontal face layer and the internal rear face layer. The intermediary sandwiched face layer may generally be made out of a polymeric material. The internal rear face layer may generally have a substantially non-uniform thickness formed via a substantially planar rear surface and a substantially non-planar frontal surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S. Provisional Application No. 62/876,432, filed on Jul. 19, 2019, the disclosure of which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a golf club head having a multi-layered striking face. More specifically, the striking face of the golf club head in accordance with the present invention is further comprised of an external frontal face layer, an internal rear face layer, and an intermediary sandwiched face layer juxtaposed between the external frontal face layer and the internal rear face layer.

BACKGROUND OF THE INVENTION

Modern day golf club design has evolved since the early days of golf. The good news of all the technological advancements in golf club technology is that it makes the game of golf easier for golfers of all skill levels. However, all these advancements come with tremendous challenges for the golf club engineer.

One of the latest trends in golf club design is the utilization of multiple different materials in the same golf club head to take advantage of the individual performance characteristics the base material, and combining them to create a better performing golf club head. U.S. Pat. No. 6,406,382 to Deshmukh et al. shows another example of utilizing multiple different materials in a golf club head. More specifically, U.S. Pat. No. 6,406,382 to Deshmukh et al. contemplates using high density components such as tungsten, copper, and/or chromium in a golf club head to help improve the weighting of a golf club head.

U.S. Pat. No. 6,440,008 to Murphy et al. even goes as far as contemplating using light density composite materials having a material thickness in the range of 0.010 to 0.250 inches to form the body portion, to help save mass from portions of the golf club head not subjected to high stresses, allowing one to take advantage of the inherent properties of each of the fundamental material.

Finally, U.S. Pat. No. 6,527,650 to Reyes et al. contemplates using both heavy density tungsten material as well as lightweight composite material all within the same golf club head to take advantage of the inherent properties of both materials to improve the performance of a golf club head.

It should be noted that although the utilization of multi-material golf club head has been around, the industry has always been perplexed by the utilization of multi-material around the striking face portion of the golf clubhead due to the high amount of stress when impacting a golf ball. The present invention focuses on a golf club head having a multi-layered multi-material striking face of a golf club head to further improve the performance of a golf club head.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a golf club head comprising of a striking face portion located at a frontal portion of the golf club head and an aft rear portion attached to the rear of the striking face portion. The striking face portion further comprises of an external frontal face layer located at an external frontal portion of the striking face portion, an internal rear face layer located at an internal rear portion of the striking face portion, and an intermediary sandwiched face layer, juxtaposed between the external frontal face layer and the internal rear face layer; wherein the internal rear face layer has a non-uniform thickness created by a substantially planar rear surface and a substantially non-planar front surface.

In another aspect of the present invention is a golf club head comprising of a striking face portion located at a frontal portion of the golf club head and an aft rear portion attached to the rear of the striking face portion. The striking face portion further comprises of an external frontal face layer located at an external frontal portion of the striking face portion, an internal rear face layer located at an internal rear portion of the striking face portion, and an intermediary sandwiched face layer, juxtaposed between the external frontal face layer and the internal rear face layer; wherein the intermediary sandwiched face layer is made out of a polymeric material having a Shore D hardness of between about 55 to 75, wherein the intermediary sandwiched face layer has a non-uniform thickness, and wherein the intermediary sandwiched face layer has a rear surface that is substantially non-planar and a frontal surface that is substantially planar.

In another aspect of the present invention is a golf club head comprising of a striking face portion located at a frontal portion of the golf club head and an aft rear portion attached to the rear of the striking face portion. The striking face portion further comprises of an external frontal face layer located at an external frontal portion of the striking face portion, an internal rear face layer located at an internal rear portion of the striking face portion, and an intermediary sandwiched face layer, juxtaposed between the external frontal face layer and the internal rear face layer; wherein the internal rear face layer has a non-uniform thickness created by a substantially planar rear surface and a substantially non-planar front surface, wherein the internal rear face layer further comprises a thickened central region and a thinned perimeter region, wherein the thickened central region of the internal rear face layer has a thickness of between about 2.0 mm to about 4.0 mm, and the thinned perimeter region has a thickness of between about 1.5 mm to about 2.5 mm, wherein the intermediary sandwiched face layer is made out of a polymeric material having a Shore D hardness of between about 55 to 75, and wherein the intermediary sandwiched face layer has a non-uniform thickness, and wherein the intermediary sandwiched face layer has a rear surface that is substantially non-planar and a frontal surface that is substantially planar, wherein the intermediary sandwiched face layer further comprises a thinned central region and a thickened perimeter region, wherein the thinned central region of the intermediary sandwiched face layer has a thickness of between about 0.4 mm to about 1.0 mm, and the thickened perimeter region has a thickness of between about 1.3 mm to about 2.1 mm, and wherein the external frontal face layer has a uniform thickness.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will be apparent from the following description of the invention as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.

FIG. 1 of the accompanying drawings shows a perspective view of a golf club head in accordance with an embodiment of the present invention;

FIG. 2 of the accompanying drawings shows an exploded perspective view of a golf club head in accordance with an embodiment of the present invention;

FIG. 3 of the accompanying drawings shows a frontal view of a golf club head in accordance with an embodiment of the present invention, allowing cross-sectional lines 4-4′ and 5-5′ to be shown;

FIG. 4 of the accompanying drawings shows a cross-sectional view of a golf club head in accordance with an embodiment of the present invention;

FIG. 5 of the accompanying drawings shows another cross-sectional view of a golf club head in accordance with an embodiment of the present invention, also identifying circular region A;

FIG. 6 of the accompanying drawings shows an enlarged cross-sectional view of circular region A shown in FIG. 5, depicting the striking face portion of a golf club head in accordance with an embodiment of the present invention;

FIG. 7 of the accompanying drawings shows an enlarged cross-sectional view of circular region A shown in FIG. 5, depicting the striking face portion of a golf club head in accordance with an alternative embodiment of the present invention;

FIG. 8 of the accompanying drawings shows an enlarged cross-sectional view of a circular region A shown in FIG. 5, depicting the striking face portion of a golf club head in accordance with an alternative embodiment of the present invention;

FIG. 9 of the accompanying drawings shows an enlarged cross-sectional view of a circular region A shown in FIG. 5, depicting the striking face portion of a golf club head in accordance with an alternative embodiment of the present invention;

FIG. 10 of the accompanying drawings shows an exploded cross-sectional view of a golf club head in accordance with a further alternative embodiment of the present invention;

FIG. 11 of the accompanying drawings shows an enlarged cross-sectional view of a circular region A shown in FIG. 5, depicting the striking face portion of a golf club head in accordance with a further alternative embodiment of the present invention;

FIG. 12 of the accompanying drawings shows an exploded cross-sectional view of a golf club head in accordance with a further alternative embodiment of the present invention;

FIG. 13 of the accompanying drawings shows an enlarged cross-sectional view of a circular region A shown in FIG. 5, depicting the striking face portion of a golf club head in accordance with an alternative embodiment of the present invention; and

FIG. 14 of the accompanying drawings shows a characteristic time plot of the various data collected from an exemplary inventive golf club head in accordance with the USGA characteristic time test.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description describes the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Various inventive features are described below and each can be used independently of one another or in combination with other features. However, any single inventive feature may not address any or all of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below.

FIG. 1 of the accompanying drawings shows a golf club head 100 in accordance with an exemplary embodiment of the present invention. Golf club head 100 shown here may have striking face portion 110 and an aft rear portion 120. Furthermore, the striking face portion 110 may even further comprise of an external frontal face layer 112, an intermediary sandwiched face layer 114, and an internal rear face layer 116. This triple layered face improves the performance of the golf club head 100 by reducing unnecessary mass from the thickest portion of the golf club, and can also improve the interaction with a golf ball by producing more consistent ball speed across the face. Although the combination and utilization of the multiple materials attributes significantly to this improvement in performance, it is not the only factor. Numerous other factors, including variations in thickness, variations in geometry, variations in material properties, and any other variations in the design can also contribute to the performance gain without departing from the scope and content of the present invention.

In order to show some of these various other factors that combine together to achieve the performance of the current inventive golf club head 100, various other figures are provided below illustrating some of these characteristics. FIG. 2 of the accompanying drawings shows an exploded perspective view of a golf club head 200 in accordance with an exemplary embodiment of the present invention. In this exploded view of the golf club head 200, we can clearly see that the golf club still has the frontal face layer 210 and an aft rear portion 220. Once again, the frontal face layer 210 of this embodiment has three sub-components, an external frontal face layer 212, an intermediary sandwiched face layer 214, and an internal rear face layer 216.

In this embodiment, we can see that the external frontal face layer 212 is generally a thin layer of metallic material such as titanium, as that is generally the preferred material used for the striking face portion of a golf club head 200. The external frontal face layer 212 may generally have a density of between about 4 grams/cc and about 5 grams/cc, more preferably between about 4.25 grams/cc and about 4.75 grams/cc, and most preferably about 4.5 grams/cc. However, it should be noted that the external frontal face layer 212 may also be made out of other metallic materials that is different from titanium such as steel, aluminum, or even composite type material all without departing from the scope and content of the present invention; so long as it is capable of withstanding the impact forces with a golf ball without cracking. This thin external frontal face layer 212 may generally fit inside an equally thin pocket 222 located at a frontal portion of the intermediary sandwiched face layer 214. The intermediary sandwiched face layer 214, as shown in this exemplary embodiment of the present invention, is generally made out of a polymeric material capable of absorbing the impact and vibration that the external frontal face layer 212 experiences when it impacts a golf ball. More information regarding the polymeric material can be found in U.S. Pat. No. 10,099,103 to Golden et al., as it relates to the discussion on polymeric filler material; the disclosure of which is incorporated by reference in its entirety. However, it should be noted that the intermediary sandwiched face layer 214 can be made out of alternate materials that fall within and outside of the polymeric material category without departing from the scope and content of the present invention so long as it has a material hardness it is between about Shore D of 55 to about Shore D of 75, more preferably between about Shore D of 60 to about Shore D of 70, more preferably shore D of 65. Finally, in this embodiment of the present invention shown in FIG. 2, the internal rear face layer 216 may contain a thicker pocket 223 adapted to engage the intermediary sandwiched face layer 214. It should be noted that in this exploded view of the present invention, it can be seen that the frontal surface of the internal rear face layer 216 may have a unique topography having at least one region of increased thickness, creating a non-uniform thickness that is created by a substantially planar rear surface and a substantially non-planar front surface. Alternatively speaking, it can be said that golf club head 200 has a central thickened portion 224 located at the geometric center of the internal rear face layer 216, surrounded by a transition region 226, and an area of thinned region 228 around the perimeter. Although not specifically shown in the exploded view in FIG. 2, the rear surface of the intermediary sandwiched face layer 214 may have a complimentary geometry to the frontal surface of the internal rear face layer 216 to ensure proper bond between the materials. FIG. 2 of the accompanying drawing shows the internal rear face layer 216 being a separate component that can be attached to the rear aft portion 220. However, this rear internal rear face layer 216 can be formed as a unitary piece with the rear aft portion 220 without departing from the scope and content of the present invention.

It should be noted here that having this three layered construction for the frontal face layers 210 is critical to the proper functionality of the present invention. More specifically, the intermediary sandwiched face layer 214 is the critical component in this embodiment, as it provides the stability to absorb the impact forces experienced by the external frontal face layer 212. Moreover, the softer and more elastic material used for the intermediary sandwiched face layer 214 further helps improve performance of the golf club head by balancing the ball speed across the face.

FIG. 3 of the accompanying drawings shows a frontal view of a golf club head 300 in accordance with an exemplary embodiment of the present invention. This frontal view of the golf club head 300 shows the multi-layered and multi-material striking face portion having the external frontal face layer 312, the intermediary sandwiched face layer 314, and the internal rear face layer 316 as previously shown. This figure, however, allows cross-sectional lines 4-4′ and 5-5′ to be shown more clearly. Cross-sectional line 4-4′ is a horizontal cross-sectional line that passes through the face center 321 in a heel to toe direction, and this cross-sectional line will further illustrate the relationship between the various striking face portion components. Similarly, cross-sectional line 5-5′ is a vertical line that passes through the face center 321 in a crown to sole direction allowing a further illustration of the various components in this orientation.

FIG. 4 of the accompanying drawings shows a cross-sectional view of a golf club head 400 in accordance with an exemplary embodiment of the present invention taken along cross-sectional line 4-4′ shown in FIG. 3. In this cross-sectional view of the golf club head 400, the various thicknesses of the external frontal face layer 412, the intermediary sandwiched face layer 414, and the internal rear face layer 416 as well as how they interface with one another is shown. Like previously mentioned, the external frontal face layer 412 is a thin layer of metallic material positioned at an external frontal portion of the golf club head 400. The external frontal face layer 412 is placed in a thin cavity within the intermediary sandwiched face layer 414, which was also previously mentioned. However, FIG. 4's cross-sectional view allows the variable thickness of the intermediary sandwiched face layer 414 to be shown more clearly. In this cross-sectional view, it can be seen that the frontal surface of the intermediary sandwiched face layer 414 is substantially flat, except for the cavity to receive the external frontal face layer 412. However, the rear surface of the intermediary sandwiched face layer 414 is substantially variable, with its thinnest portion near the face center, and the thickest portion around the perimeter; more specifically the heel and toe portion as shown in FIG. 4. Finally, the cross-sectional view of golf club head 400 shown in FIG. 4 illustrates an internal rear face layer 416 having a thicker pocket that is capable of accepting the intermediary sandwiched face layer 414. It should be noted that the thicker pocket may generally have a frontal surface that creates a variable thickness frontward, having a thickened central region, a transition region, and a thinned perimeter as previously discussed.

FIG. 5 of the accompanying drawings shows a cross-sectional view of golf club head 500 in accordance with an exemplary embodiment of the present invention taken along cross-sectional line 5-5′ shown in FIG. 3. This cross-sectional view of the golf club head 500 shows a very similar geometry of the various components in a crown to sole cross-section as it did in the heel to toe cross-section. The components, external frontal face layer 512, intermediary sandwiched face layer 514, and the internal rear face layer 516 all have a similar shape and geometry in this cross-sectional orientation as it did in the orientation presented in FIG. 4. In order to provide a clearer view of the various face component, an enlarged cross-sectional view of the golf club head 500 around circular region A is provided in FIG. 6.

FIG. 6 of the accompanying drawings shows an enlarged cross-sectional view of a golf club head 600 that's focused on enlarging and showing the detail of a golf club head 600 in a region identified by circular region A shown in FIG. 5. This enlarged cross-sectional view of golf club head 600 allows the various dimensions of the face components to be shown in more detail, along with their respective thicknesses. More specifically, the external frontal face layer 612 shown in this embodiment of the present invention may generally be relatively thin, having a thickness d1 that is less than about 0.8 mm, more preferably less than about 0.7 mm, and most preferably less than about 0.6 mm. The intermediary sandwiched face layer 614 shown in this embodiment of the present invention may have a thickness d2 of between about 0.4 mm and about 1.0 mm around the thinned central region, more preferably between about 0.4 mm and about 0.8 mm, and most preferably between about 0.4 mm and about 0.6 mm. The intermediary sandwiched face layer 614 at its thickened perimeter portion may have a thickness d2 of between about 1.3 mm and about 2.1 mm, more preferably between about 1.5 mm and about 1.9 mm, and most preferably about 1.7 mm. The internal rear face layer 616 as shown in this embodiment of the present invention, as previously mentioned, may have a substantially flat rear surface combined with a substantially non-planar front surface. This internal rear face layer 616 has a thickness d3 around the thinned perimeter region of between about 1.5 mm to about 2.5 mm, more preferably between about 1.7 mm to about 2.3 mm, and most preferably about 1.9 mm. At the thickened central portion, the internal rear face layer 616 may generally have a thickness d3 of between about 2.0 mm to about 4.0 mm, more preferably between about 2.2 mm to about 3.8 mm, and most preferably between about 2.4 mm to about 3.1 mm.

FIG. 7 of the accompanying drawings shows an enlarged cross-sectional view of a golf club head 700 in accordance with an alternative embodiment of the present invention, enlarging a portion of a golf club head 700 shown by circular region A shown in FIG. 5. Although most of the design within this embodiment of the present invention is very similar to previous embodiments previously discussed, there are several distinguishing features worth identifying. First and foremost, it can be seen that the internal rear face layer 716 is now formed out of two sub-components, a face insert 716 a, and a perimeter portion 716 b, both of which combine to create the internal rear face layer 716. Secondly, it can be seen that the interface between the external frontal face layer 712 and the intermediary sandwiched face layer 714 is slightly different. More specifically, the intermediary sandwiched face layer 714 no longer contains a pocket 222 (shown in FIG. 2) to engage a substantially planar shaped external frontal face layer 212 (shown in FIG. 2 and FIG. 6). In this alternative embodiment of the present invention, the external frontal face layer 712 is substantially C shaped, and wraps around both the intermediary sandwiched face layer 714 as well as the internal rear face layer 716. This embodiment of the present invention may be preferred to protect the softer intermediary sandwiched face layer 714 by ensuring that it is not exposed externally. Although in previous embodiments of the present invention, the exposed intermediary sandwiched face layer 614 is shifted towards the perimeter to avoid portions of the golf club head 600 that is normally exposed to contact with a golf ball, this present embodiment completely insulates the more fragile intermediary sandwiched face layer 714 from any accidental damage.

It should be noted here that in this embodiment of the present invention, wherein the intermediate sandwiched face layer 714 is completely shielded from any external exposure, the polymeric material used to create the intermediate sandwiched face layer 714 could be made from a softer material than what is previously mentioned. More specifically, in this alternative embodiment of the present invention, the polymeric material for the intermediate sandwiched face layer 714 may have a Shore A hardness of between about 65 to about 90, more preferably a Shore A hardness of between about 70 to about 85, and most preferably a Shore A hardness of about 77.

FIG. 8 of the accompanying drawings shows an enlarged cross-sectional view of a golf club head 800 in accordance with an alternative embodiment of the present invention, enlarging a portion of a golf club head 800 shown via circular region A shown in FIG. 5. In this alternative embodiment of the present invention, the striking face portion is still comprised out of three layers, an external frontal face layer 812, an intermediary sandwiched face layer 814, and an internal rear face layer 816. However, this embodiment differs from the previous embodiments in the following ways. More specifically, golf club head 800, similar to previous embodiments, has a relatively thin external frontal face layer 812 intended to make contact with a golf ball. The intermediary sandwiched face layer 814, however, differs from the previous embodiments in two very significant ways. First and foremost, the intermediary sandwiched face layer 814 is of substantially constant thickness, as the frontal surface of the internal rear face layer 816 is no longer variable. Secondly, the intermediary sandwiched face layer 814 being substantially constant thickness means that there are no pockets to receive the external frontal face layer 812, eliminating any exposure of the intermediary sandwiched face layer 814 away from the contact surface only the leading edge portion of the crown and sole. Finally, the internal rear face layer 816 of golf club head 800 may have a variable thickness, but it is located on the rear surface, creating a substantially flat frontal surface. This embodiment may be preferred for the ease of constructing the various layers, but could have some challenges associated with the bonding of the various layers.

FIG. 9 of the accompanying drawings shows an enlarged cross-sectional view of a golf club head 900 in accordance with an alternative embodiment of the present invention, enlarging a portion of a golf club head 900 shown via circular region A shown in FIG. 5. This embodiment of the present invention, although still having the three layered striking face portion that is core to the present invention, presents a slightly different construction. In this alternative embodiment of the present invention, the thin external frontal face layer 912 remains the same. However, instead of a thin pocket being created by the intermediary sandwiched face layer, the present invention utilizes an oversized pocket in the internal rear face layer 916, that is capable of receiving both the intermediary sandwiched face layer 914 as well as the external frontal face layer 912. This construction achieves the same objective previously mentioned about protecting the fragile internal sandwiched layer 914 in an oversized pocket that could make it easier to manufacture.

FIGS. 10 and 11 show an exploded view and an enlarged cross-sectional view of a golf club head 1000 in accordance with an alternative embodiment of the present invention, with the enlarged cross-sectional view illustrating the features of golf club head 1000 shown in circular region A in FIG. 5. In this alternative embodiment of the present invention, the internal rear face layer 1016 may be in the shape of a face insert, and have a slightly different frontal face topography having three regions of increased thickness 1024, with a toe region of increased thickness 1024 a, a central region of increased thickness 1024 b, and a heel region of increased thickness 1024 c. This alternative topography in the frontal portion may help balance the ball speed of the striking face portion of the golf club head 1000. The cross-sectional view of the golf club head 1000 shown in FIG. 11 shows the same three layered striking face portion, but in this embodiment of the present invention, the perimeter of the thin external frontal face layer 1012 leaves a gap with the internal rear face layer 1016 round the perimeter of the golf club head 1000 to prevent direct contact between those two components. Separating the external frontal face layer 1012 and the internal rear face layer 1016 leaves the intermediary sandwiched face layer 1014 as the only medium between these two components.

FIGS. 12 and 13 show an exploded view and an enlarged cross-sectional view of a golf club head 1200 in accordance with an alternative embodiment of the present invention, with the enlarged cross-sectional view illustrating the features of golf club head 1200 shown in circular region A in FIG. 5. This alternative embodiment of the present invention shows an even further alternative topography for the frontal surface of the internal rear face layer 1216. More specifically, this golf club head 1200 has an internal rear face layer 1216 with a frontal topography that contains six regions of increased thickness 1224, a first region of increased thickness 1224 a, a second region of increased thickness 1224 b, a third region of increased thickness 1224 c, a fourth region of increased thickness 1224 d, a fifth region of increased thickness 1224 e. and a sixth region of increased thickness 1224 f. The locations of the regions of increased thickness relative to one another is strategically determined based on the specific performance of the golf club head 1200. The cross-sectional view of the golf club head 1200 allows the frontal topography of the internal rear face layer 1216 to be shown more clearly. Golf club head 1200 in accordance with this embodiment of the present invention also leaves a gap between the external frontal face layer 1212 and the internal rear face layer 1216, leaving the intermediary sandwiched face layer 1214 as the only medium between these two components.

Despite all of the benefits of improved performance and mass savings described above, utilizing this three layered striking face offers additional advantages as it relates to the Characteristic Time (CT) of a golf club head. CT, as currently known in the golfing industry, may generally relate to the amount of time a pendulum contacts the striking face of a golf club head after being dropped from various height that simulates different velocities. The velocity and time values, captured by an accelerometer attached to the pendulum, are then generally plotted against a function of the velocity. A linear trend line having a specific slope may be formed by the various data points, and the ultimate y-intercept may yield the CT value of the golf club head. More details regarding the exact apparatus and procedure used to acquire the CT value of a golf club head may be found in U.S. Pat. No. 6,837,094 to Pringle et al ('094 Patent), the disclosure of which is incorporated by reference in its entirety.

FIG. 14 of the accompanying drawings shows a graphical representation of the various contact time results taken using the portable apparatus for measuring the flexibility of the striking face of a golf club head according to the steps described in the '094 Patent. More specifically, FIG. 14 shows the characteristic time results of the striking face of an exemplary golf club head in accordance with the current invention being plotted on the y-axis against the velocities of the pendulum at each of the respective data points 1462 being plotted on the x-axis. It should be noted that the velocities of the pendulum taken by an accelerometer attached to the pendulum is taken to an exponent value of −0.329 in order to minimize the expected errors on the intercept value to create a linear relationship quantified by the Equation (1) below.

T=A+BV ^(−k)  Eq. (1)

Wherein T equals the time for the velocity of the pendulum to rise from 5% to 95% of the maximum velocity recorded, B is the slope of the trend-line 1464 formed by the various data points 1462, V is the velocity of the pendulum test at the various data points 1462, and k is the exponential adjustment factor to minimize the error in the intercept value of the golf club head. The intercept between the trend-line 1464 and the y-axis, identified here as A, can be determined from the T, B, and V values above and may generally be the ultimate CT values used by the USGA which correlates to the ability of the golf club head to flex during impact with a golf ball.

It is worth noting here that, because the CT value here is determined based on the intercept A, the slope B of the trend-line 1464 formed by the various CT results of each individual data point 1462 from the pendulum test is an important factor that greatly affects the CT value. Because the current invention utilizes a three layered face construction having an intermediary sandwiched face layer that is made out of a polymeric material having a softer durometer, the slope B of the trend-line 1464 created by the various data points may generally be steeper than the slope of a traditional prior art golf club head. More specifically, the slope formed from the trend-line 1464 of the various data points 1462 may be known here at the “characteristic time slope”. The “characteristic time slope”, as defined in the current invention above, may generally be greater than about 5 and less than about 50, more preferably greater than about 10 and less than about 45, even more preferably greater than about 12.5 and less than about 30, and most preferably greater than about 15 and less than about 20 as shown in FIG. 14. Although the units of the slope of the characteristic time slope trend-line 1464 is not specifically discussed above, it can may generally be derived by dividing the units for the time in microseconds by the value of the velocity to the −0.33 power. The end results of the unit for the trend-line 1464 may generally be (microseconds/(seconds/meters)) or any other simplified form of that equation all without departing from the scope and content of the present invention. More information regarding the CT test, as defined and performed by the United States Golf Association (USGA), can be found in the Technical Description of the Pendulum Test, Revised Version, Discussion of Points Raised During Notice & Comment Period (November 2003), the disclosure of which is incorporated by reference in its entirety. More details regarding this CT discussion may be found in U.S. Pat. No. 8,221,261 to Curtis et al., the disclosure of which is also incorporated by reference in its entirety.

Other than in the operating example, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, moment of inertias, center of gravity locations, loft, draft angles, various performance ratios, and others in the aforementioned portions of the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear in the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the above specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.

It should be understood, of course, that the foregoing relates to exemplary embodiments of the present invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. 

1. A golf club head comprising: a striking face portion located at a frontal portion of said golf club head; said striking face portion further comprises; an external frontal face layer located at an external frontal portion of said striking face portion; an internal rear face layer located at an internal rear portion of said striking face portion; and an intermediary sandwiched face layer, juxtaposed between said external frontal face layer and said internal rear face layer, an aft rear portion attached to the rear of said striking face portion; wherein said internal rear face layer has a non-uniform thickness created by a substantially planar rear surface and a substantially non-planar front surface wherein said intermediary sandwiched face layer further comprises a thinned central region and a thickened perimeter region, and wherein said thinned central region of said intermediary sandwiched face layer has a thickness of between about 0.4 mm to about 1.0 mm, and said thickened perimeter region has a thickness of about 1.7 mm.
 2. The golf club head of claim 1, wherein said intermediary sandwiched face layer completely separates said external front face layer from said internal rear face layer.
 3. The golf club head of claim 1, wherein said intermediary sandwich face layer is made out of a polymeric material.
 4. The golf club head of claim 1, wherein said intermediary sandwiched face layer is made out of a polymeric material having a Shore D hardness of between about 55 to about
 75. 5. The golf club head of claim 4, wherein said polymeric material of said intermediary sandwiched face layer has a Shore D hardness of between about 60 to about
 70. 6. The golf club head of claim 5, wherein said polymeric material of said intermediary sandwiched face layer has a Shore D hardness of about
 65. 7. The golf club head of claim 1, wherein said intermediary sandwiched face layer has a non-uniform thickness.
 8. The golf club head of claim 1, wherein said intermediary sandwiched face layer has a rear surface that is substantially non-planar.
 9. The golf club head of claim 8, wherein said intermediary sandwiched face layer has a frontal surface that is a substantially planar.
 10. The golf club head of claim 8, wherein said intermediary sandwiched face layer has a frontal surface that is substantially non-planar, forming a pocket.
 11. The golf club head of claim 1, wherein said external frontal face layer has a substantially uniform thickness. 12-14. (canceled)
 15. The golf club head of claim 1, wherein said thinned central region of said intermediary sandwiched face layer has a thickness of between about 0.4 mm to about 0.6 mm, and said thickened perimeter region has a thickness of about 1.7 mm.
 16. A golf club head comprising: a striking face portion located at a frontal portion of said golf club head; said striking face portion further comprises; an external frontal face layer located at an external frontal portion of said striking face portion; an internal rear face layer located at an internal rear portion of said striking face portion; and an intermediary sandwiched face layer, juxtaposed between said external frontal face layer and said internal rear face layer, an aft rear portion attached to the rear of said striking face portion; wherein said intermediary sandwiched face layer is made out of a polymeric material having a Shore D hardness of between about 55 to 75, wherein said intermediary sandwiched face layer has a non-uniform thickness, wherein said intermediary sandwiched face layer has a rear surface that is substantially non-planar and a frontal surface that is substantially planar, wherein said intermediary sandwiched face layer further comprises a thinned central region and a thickened perimeter region, and wherein said thinned central region of said intermediary sandwiched face layer has a thickness of between about 0.4 mm to about 1.0 mm, and said thickened perimeter region has a thickness of between about 1.5 mm to about 1.9 mm.
 17. The golf club head of claim 16, wherein said polymeric material of said intermediary sandwiched face layer has a Shore D hardness of between about 60 to about
 70. 18. The golf club head of claim 17, wherein said polymeric material of said intermediary sandwiched face layer has a Shore D hardness of about
 65. 19. The golf club head of claim 17, wherein said intermediary sandwiched face layer further comprises a thinned central region and a thickened perimeter region, and wherein said internal rear face layer has a non-uniform thickness created by a substantially planar rear surface and a substantially non-planar front surface.
 20. A golf club head comprising: a striking face portion located at a frontal portion of said golf club head; said striking face portion further comprises; an external frontal face layer located at an external frontal portion of said striking face portion; an internal rear face layer located at an internal rear portion of said striking face portion; and an intermediary sandwiched face layer, juxtaposed between said external frontal face layer and said internal rear face layer, an aft rear portion attached to the rear of said striking face portion; wherein said internal rear face layer has a non-uniform thickness created by a substantially planar rear surface and a substantially non-planar front surface, wherein said internal rear face layer further comprises a thickened central region and a thinned perimeter region, wherein said thickened central region of said internal rear face layer has a thickness of between about 2.0 mm to about 4.0 mm, and said thinned perimeter region has a thickness of between about 1.5 mm to about 2.5 mm, wherein said intermediary sandwiched face layer is made out of a polymeric material having a Shore D hardness of between about 55 to 75, and wherein said intermediary sandwiched face layer has a non-uniform thickness, wherein said intermediary sandwiched face layer has a rear surface that is substantially non-planar and a frontal surface that is substantially planar, wherein said intermediary sandwiched face layer further comprises a thinned central region and a thickened perimeter region, wherein said thinned central region of said intermediary sandwiched face layer has a thickness of between about 0.4 mm to about 1.0 mm, and said thickened perimeter region has a thickness of between about 1.3 mm to about 2.1 mm, and wherein said external frontal face layer has a uniform thickness. 